You've probably always wanted to enjoy the evening with a glass of wine. Your sub is of course responsible for serving the drink. Now it's possible in style.
The best thing, of course, is to enjoy it in a small group, where everyone has their sub kneeling next to them and the Doms' conversation is not disturbed by unauthorized interruptions, which are very popular with Brats.
You can also send your sub to the bar at a party to get you a drink. Depending on your sub's nonverbal communication skills, you may want to consider paper and pen.
You probably already have your own ideas about where this useful part can be used.